The present invention relates to a belt for a continuously variable transmission, including a large number of metal elements supported on metal ring assemblies each of which is comprised of a plurality of endless metal rings laminated one on another, and particularly, to a metal element structure thereof.
As shown in FIG. 14, in a belt-type continuously variable transmission including a metal belt 03 wound around a drive pulley 01 and a driven pulley 02, a stationary pulley half 04 of the drive pulley 01 and a stationary pulley half 05 of the driven pulley 02 are disposed at diagonal positions, and a movable pulley half 06 of the drive pulley 01 and a movable pulley half 07 of the driven pulley 02 are disposed at diagonal positions. Therefore, when the movable pulley halves 06 and 07 of the drive pulley 01 and the driven pulley 02 are moved toward or away from the stationary pulley halves 04 and 05, the center line La of a V-groove in the drive pulley 01 and the center line Lb of a V-groove in the driven pulley 02 are not aligned with each other to produce a small misalignment xcex1 (which is usually of 1 mm or less).
A belt-type continuously variable transmission is conventionally known from Japanese Patent Application Laid-open No. 4-362338, in which to wind the metal belt 03 around the drive pulley 01 and the driven pulley 02 with the misalignment a absorbed, at least one of the front and rear contact surfaces of the metal elements 08 constituting the metal belt 03 is formed into an arcuate shape, thereby making a relative yawing possible between the metal elements 08 which are in contact with each other.
Further, a belt-type continuously variable transmission is disclosed in Japanese Utility Model Application Laid-open No. 63-33046, in which the thickness of a metal element from its outer periphery to an outer periphery side of the pitch line is large, so that the metal element has a wedge-shaped section.
It should be noted here that the metal belt 03 of the belt-type continuously variable transmission described in Japanese Patent Application Laid-open No. 4-362338 is formed to transmit a driving force by a compressing force applied between the metal elements 08 which are in contact with each other at contact surfaces thereof. In a conventional metal belt including metal elements 08 of which contact surfaces are formed into an arcuate shape, however, the attitude of the metal elements 08 in a yawing direction is unstable and for this reason, there is a possibility that the movement of the metal belt 03 in a zigzag direction may be promoted, whereby the efficient transmission of a power may be impeded.
Further, in the belt-type continuously variable transmission disclosed in Japanese Utility Model Application Laid-open No. 63-33046, there are such problems that the formation of the wedge-shaped section of the metal element is difficult, and that the movement of the metal element is unstable, because the pitch lines are separated in a chord portion of a metal belt.
The present invention has been accomplished with the above circumstances in view, and it is an object of the present invention to ensure that the absorption of a misalignment between the drive pulley and the driven pulley and the prevention of the zigzag movement of the metal belt are reconciled in the metal belt for the belt-type continuously variable transmission.
To achieve the above object, according to the present invention, there is provided a belt for a continuously variable transmission, comprising a large number of metal elements supported on metal ring assemblies each of which is comprised of a plurality of endless metal rings laminated one on another, the belt being wound around a drive pulley and a driven pulley to transmit a driving force between both of the pulleys, characterized in that each of the metal elements includes a ring slot into which the metal ring assembly is fitted, an element body portion located on a radially inner side of the ring slot, and an element head portion located on a radially outer side of the ring slot, the element body portion and the element head portion being formed with contact surfaces, respectively, at which adjacent ones of the metal elements can contact with each other, a lateral width of the contact surface of the element body portion being smaller than a lateral width of the contact surface of the element head portion.
With the above arrangement, in a chord portion of the metal belt extending from the drive pulley to the driven pulley, the adjacent metal elements are brought into contact with each other at least on contact surfaces of the element head portions located on the radially outer side to transmit the driving force. At this time, the adjacent metal elements can be brought into close contact with each other without yawing by virtue of the contact surfaces of the element head portions having the large lateral width to reliably transmit the driving force. The misalignment between the drive pulley and the driven pulley can be absorbed by the lateral sliding movement of the contact surfaces of the element head portions on each other. Moreover, in a pulley-wound zone in which the metal elements are wound around the drive pulley and the driven pulley, the adjacent metal elements are in contact with each other on the contact surfaces of the element body portions located on the radially inner side, but at this time, the relative yawing movement between the adjacent metal elements is permitted by virtue of the contact surfaces of the element body portions having the small lateral width. Thus, the inclination of the metal elements in the yawing direction can be corrected, and the metal elements can be wound in a correct attitude around the drive pulley and the driven pulley, thereby avoiding the generation of abnormal wearing of the pulleys and the metal elements.
Further, in the chord portion in which an urging force is generated between the metal elements, the surface pressure on the element body portions which contact with each other over a narrow area is higher than that on the element head portions which contact with each other over a wide area. For this reason, the element body portion is largely distorted, as compared with the element head portion, whereby the sectional shape of the metal element is deformed into a wedge shape. As a result, the plurality of metal elements are curved radially outwards and connected together in the chord portion of the metal belt and hence, the inner peripheral surfaces of the ring slots of the metal elements are urged radially inwards by the metal ring assemblies, whereby the rolling of the metal elements is prevented.
Moreover, because the contact surface of the element head portion which is a main contact surface is formed on the element head portion having a relatively simple flat plate shape rather than on the element body portion having a relatively complicated three-dimensional shape, it is convenient for the machining thereof.
Here, the term xe2x80x9clateralxe2x80x9d is defined as a direction perpendicular to the rotating plane of the pulley, and the terms xe2x80x9cradially inner sidexe2x80x9d and xe2x80x9cradially outer sidexe2x80x9d are defined as being with respect to the rotating axis of the pulley.
In addition to the above arrangement, there is provided a belt for a continuously variable transmission, wherein the adjacent ones of the metal elements are located relative to each other by fitting of a projection and a recess, formed on one and the other of front and rear surfaces thereof, with each other.
With the above arrangement, when the metal elements have been moved to a position near the driven pulley in the chord portion of the metal belt extending from the drive pulley to the driven pulley, the adjacent ones of the metal elements are located relative to each other by fitting of the projection and the recess with each other. Therefore, succeeding metal elements can be slid laterally and arranged relative to the metal elements which have been wound around the driven pulley and constrained laterally, whereby the misalignment between the drive pulley and the driven pulley can be reliably absorbed.
Here, the front surface and rear surface of the metal element are defined as front and rear surfaces of the metal element in the direction of movement thereof.